Formic acid has long been playing an important role as a material for synthesis of various chemical substances such as pharmaceutical products and agricultural pesticides. Besides, as proposed by the present inventors by means of Patent Document 1, formic acid is important also as a material for production of hydrogen. There are known various methods for producing formic acid, including a method for producing formic acid from carbon dioxide and hydrogen (Patent Document 2, for example). However, Patent Document 2 proposes the reaction of carbon dioxide in a supercritical state (critical point: pressure of 73.3 bar, temperature of 31° C.) with hydrogen in the presence of a metal catalyst (group VIII transition metal complex) and an excess amount of basic substance, and therefore the method disclosed therein has following limitations: The method requires that the production facility have high pressure resistance and requires a separation process for the basic substance from the formic acid produced.